*2.1. Study Area*

The study area covers 17 populated offshore islands (within approximately 30 nautical miles) in the western sea area of Guangdong Province (Figure 1). The largest island in the study area is Donghai Island, with an area of 286 km2, and the smallest island is Gonggang Island, with a mere area of 1.26 km2, and all the islands are located at a distance of about 0.4 km~18 km from the coastline. The study area belongs to the subtropical climate. Compared with the coastwise mainland, the islands have an oceanic climate, with an annual temperature of 1~1.5 ◦C lower than that of the adjacent mainland; the number of days with at least Level-8 gale on annual average is 3~8 times that of the adjacent mainland; the annual amount of evaporation is 20~200 mm higher than that of the adjacent mainland [33].

**Figure 1.** Distribution map of island in the western sea area of Guangdong Province.
